Internal combustion engine having engine cover

ABSTRACT

Internal combustion engine having one or more cylinders and an engine cover encircling the cylinders with a space for defining a cooling air passage therebetween. The engine cover is made of a non-metallic resilient material such as rubber or resinous material and secured to the engine. The engine cover is formed at its inside surface with one or more projections which are adapted to be fitted to the spaces between cylinder cooling fins.

The present invention relates to internal combustion engines and moreparticularly to internal combustion engines having engine coversattached thereto.

In air-cooled internal combustion engines for snow mobiles andcultivators, it has been common to provide engine covers for the purposeof protecting the engine cylinders. Such engine covers are made of metalsheets and encircle the engine cylinders with cooling air passagesdefined between the engine cylinders and the engine covers. They aresecured to the engines usually by means of bolts or studs.

In known internal combustion engines of this type, it has beenexperienced that the engine covers vibrate in resonance to the vibrationof the engines and produce noticeable noise. Further, cyclic stresspossibly applied to the engine cover due to such vibration may decreasethe life of the engine cover. Such metal covers are furtherdisadvantageous in that they increase the weights of engines.

The present invention has therefore an object to provide an internalcombustion engine having an engine cover which does not produceappreciable noise as in conventional engine covers.

Another object of the present invention is to provide an engine coverwhich is durable and moreover small in weight.

According to the present invention, the above and other objects can beaccomplished by an internal combustion engine comprising crankcasemeans, cylinder means connected with said crankcase means, piston meansdisposed in said cylinder means, engine cover means encircling at leasta part of said cylinder means and secured to said engine, said enginecover means being made of non-metallic resilient material. According tothe present invention, use may be made of rubber material such asnitrile rubber or ethylene-propylene rubber, and resinous material suchas polyamide resin and epoxy resin for the engine cover means. Where thepresent invention is applied to an air-cooled engine, a cooling airpassage is defined between the engine cylinder means and the covermeans. The cover means may be provided at its inner surface with one ormore projections or ridges which may be fitted to the spaces definedbetween adjacent cooling fins on the cylinder means.

The above and other objects and features of the present invention willbecome apparent from the following descriptions of a preferredembodiment taking reference to the accompanying drawings, in which:

FIG. 1 is a perspective view of an internal combustion engine inaccordance with one embodiment of the present invention; and

FIG. 2 is a partially sectioned side view of the engine shown in FIG. 1.

Referring now to the drawings, the engine shown therein includes acrankcase 1 for accommodating a crankshaft (not shown) as well known inthe art. On the crankcase 1, there are mounted a plurality of cylinders2 having cooling fins 11 which may be of conventional form. A cylinderhead 3 is secured to each of the cylinders 2 and has a plurality ofcooling fins 11. Each cylinder 2 accommodates a piston 5 forreciprocating movement therein and an ignition spark plug 4 is providedon each cylinder head 3. At one side of the crankcase 1, there isprovided a starter and fan casing 9.

An engine cover 8 is attached to the engine by means of screws 10 so asto encircle the cylinders 2 and the cylinder heads 3 with spaces betweenthe cover 8 and the cylinders 2 and the cylinder heads 3 for defining acooling air passage. The engine has a cooling air fan which is disposedin the casing 9 and may be driven by the engine crankshaft through abelt or any other suitable means for blowing air toward the enginecylinders. The engine cover 8 is formed at a portion remote from the fan6 with a cooling air outlet opening 7.

The engine cover 8 is made of resilient material such as a rubber or aresinous material. The cover 8 has on the inner surface a plurality ofprojections 12 which are adapted to be fitted to the spaces between thecooling fins 11. Since the engine cover 8 is made of a resilientmaterial, there will be the least possibility of noise being producedthrough vibrations of the engine cover 8 which may be produced due toresonance of the cover with the vibrations of the engine itself.Further, the inside projections of the cover 8 are fitted to the spacesbetween the fins 11 on the cylinders 2 and the cylinder heads 3 so thatthey function as dampers between the engine cover and the fins andfirmly hold the engine cover. Since such fin dampers are manufacturedintegrally with the engine cover, it is possible to decrease the costsfor production and for assembling the cover on the engine. The enginecover made of a resilient material is further advantageous over aconventional sheet metal engine cover in respect of weight.

The invention has thus been shown and described with reference to aspecific embodiment, however, it should be noted that the invention isin no way limited to the details of the illustrated structures butchanges and modifications may be made within the scope of the appendedclaims.

We claim:
 1. An air cooled internal combustion engine comprisingcrankcase means, cylinder means having horizontally extending outsidecooling fins connected with said crankcase means, cylinder head meanshaving vertically extending outside cooling fins connected with saidcylinder means, piston means reciprocally mounted in said cylinder meansand engine cover means encircling a substantial part of both of saidhorizontally and vertically extending cooling fins and secured to saidengine to define cooling passages between the cover means, the cylindermeans and the cylinder head means, said engine cover means beingintegrally made solely of non-metallic resilient material and havinghorizontal projection means along its inside side surface to interfitwith said horizontal fins and vertical projection means along its insidetop surface to interfit with said vertical fins, said cover means havingan air intake passage at one end and an air exit passage remotelylocated therefrom to define said cooling passage means, said cover meansacting to suppress vibrations and engine noise.
 2. An air cooledinternal combustion engine comprising crankcase means, cylinder meanshaving outside cooling fin means connected with said crankcase means,cylinder head means having outside cooling fin means, piston meansdisposed in said cylinder means, engine cover means encircling asubstantial part of both said cylinder and cylinder head cooling finmeans and secured to said engine to define cooling passage means betweenthe cover means and the cylinder and the cylinder head means, saidengine cover means being integrally made solely of non-metallicresilient material and having projection means along its inside surfaceinterfitted with said cooling fin means to thereby suppress vibrationsof the cover means and engine noise.
 3. An engine in accordance withclaim 2 in which said engine cover means is made of rubber.
 4. An enginein accordance with claim 2 in which said engine cover means is made ofresinous material.
 5. An engine in accordance with claim 1 in which saidprojection means is fitted to spaces defined in said cooling fin means.6. An engine in accordance with claim 1 which includes air inlet meansfor introducing cooling air flow into cooling air passage means definedbetween said cooling fin means and said engine cover means and havingair outlet opening means for allowing the cooling air flow which haspassed through the passage means to flow out of the passage means. 7.The engine of claim 6 including fan means in one of said air inlet meansand air outlet opening means for forcing air through the cooling airpassage means.